Where is the cannon on super villain island?

Answer 1

There are several in Captain Crawfish's dream, on the ship he has in a bottle. Once you have the shrinking potion (from Black Widow's dream), you can enter the bottle, lock up the two cannons on the sails, and fire off the one in the small boat near the bottom.

Climb up behind the two cannons on the sails, and click the wooden boxes to lock them in. Go to the dinghy on the side of the boat. Wait until the pirate and cannon move away to the left, then fire the cannon to break the bottle.